#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
using namespace std;

const ll N = 1e6 + 10, INF = 0x3f3f3f3f;

ll n, m;
vector<ll> a;
priority_queue <ll> q;

void solve()
{
    cin >> n >> m;
    for (ll i = 1;i <= n;i++) { ll x; cin >> x; a.push_back(x); }
    sort(a.begin(), a.end());
    a.erase(unique(a.begin(), a.end()), a.end());
    for (ll i = 1;i < a.size();i++) q.push(a[i] - a[i - 1]);

    ll ans = a.back() - a.front();
    m--;
    while (!q.empty() && m--) {
        ans -= q.top();
        q.pop();
    }
    cout << ans << '\n';
}

signed main()
{
    // ios::sync_with_stdio(0);
    // cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    ll T = 1;
    //cin>>T;
    for (ll i = 1;i <= T;i++) {
        solve();
    }
}